This invention relates to the field of thermal imaging apparatus, in which infrared radiation is converted into a picture accessible to the user of the apparatus.
One major field of use of the invention is in forward looking infrared (FLIR) systems, which are primarily used for night vision. Prior art systems, referred to as Common Module FLIRs, are designed to use infrared detection to permit an operator to, in effect, "see" and identify objects which would otherwise be invisible. Such a system employs a mechanically scanned line array of photoconductive mercury-cadmium-telluride (MCT) detectors cooled to approximately 77.degree. K. The term "common module" refers to the requirement that each major component of the system be replaceable by an equivalent module.
In the "Preliminary Common Module Design Handbook" published by Magnavox, the following common module FLIR elements are listed: (1) Detector, comprising an array of 180 vertically oriented elements of Mercury Cadmium Telluride (HgCdTe); (2) IR (infrared) Imager, which directs infrared inputs toward the detector; (3) Scanner, which is a mechanically oscillating mirror sequentially directing infrared inputs onto the linear detector array; (4) Scan and Interlace Electronics, which provides mirror motion drive; (5) Cooler, which maintains the detectors at approximately 77.degree. K.; (6) Preamplifiers, which provide a 70 to 1 amplification of the electronic output signals of the detectors; (7) Post Amplifiers, which further amplify the detector output signals; (8) LED Display, which converts the amplified detector output signals into visible light, which is collimated by a Visual Collimator module and returned to the reflecting back surface of the scan mirror; and (9) Image Intensifier, which receives the scanned LED display output, intensifies it, and directs it to a bicular eyepiece.
The complexity and costliness of the present FLIR systems is apparent from the extensive number of major components. Also, they have significant performance limitations.
The present invention is intended to significantly reduce the cost and improve the performance of thermal imaging apparatus.